chore(ci): upgrade Gradle to 9.6.0 across workflows, Docker builds, and wrapper (#6790)

# Description of Changes

## What was changed

- Updated all GitHub Actions workflows using Gradle from older versions
(9.3.1 and 9.5.1) to Gradle 9.6.0.
- Updated the Gradle Wrapper distribution URL to use Gradle 9.6.0.
- Updated all Gradle-based Docker build stages to use the
`gradle:9.6.0-jdk25` image and corresponding image digest.
- Aligned CI, Docker, and local development environments on the same
Gradle version.
- Included the regenerated `gradlew` script changes produced by the
Gradle wrapper update process.

## Why the change was made

- Ensures consistent Gradle versions across local development, CI
workflows, and Docker builds.
- Takes advantage of the latest Gradle 9.6.0 improvements, fixes, and
compatibility updates.
- Reduces the risk of version mismatches causing build or deployment
inconsistencies.
- Simplifies maintenance by standardizing the build toolchain throughout
the repository.

---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have run `task check` to verify linters, typechecks, and tests
pass
- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#7-testing)
for more details.

.github/workflows/PR-Demo-Comment-with-react.yml

@@ -222,7 +222,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
 
       - name: Install Task
         uses: go-task/setup-task@01a4adf9db2d14c1de7a560f09170b6e0df736aa # v2.1.0

.github/workflows/ai-engine.yml

@@ -43,7 +43,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
 
       - name: Install Task
         uses: go-task/setup-task@01a4adf9db2d14c1de7a560f09170b6e0df736aa # v2.1.0

.github/workflows/backend-build.yml

@@ -58,7 +58,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
           cache-disabled: true
 
       - name: Install Task

.github/workflows/check-licence.yml

@@ -40,7 +40,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
           cache-disabled: true
 
       - name: Install Task

.github/workflows/check-openapi.yml

@@ -45,7 +45,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
           cache-disabled: true
 
       - name: Install Task

.github/workflows/coverage-aggregate.yml

@@ -51,7 +51,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.3.1
+          gradle-version: 9.6.0
           cache-disabled: true
 
       - name: Set up Python

.github/workflows/db-migration-test.yml

@@ -48,7 +48,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
           cache-disabled: true
 
       # No `-PnoSpotless` here yet because the upstream cache layer matches the

.github/workflows/docker-compose-tests.yml

@@ -61,7 +61,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
           cache-disabled: true
 
       - name: Set up Docker Buildx

.github/workflows/frontend-backend-licenses-update.yml

@@ -349,7 +349,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
 
       - name: Install Task
         uses: go-task/setup-task@01a4adf9db2d14c1de7a560f09170b6e0df736aa # v2.1.0

.github/workflows/multiOSReleases.yml

@@ -73,7 +73,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
 
       - name: Install Task
         uses: go-task/setup-task@01a4adf9db2d14c1de7a560f09170b6e0df736aa # v2.1.0
@@ -148,7 +148,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
 
       - name: Setup Node.js
         if: matrix.variant.build_frontend == true
@@ -252,7 +252,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
 
       - name: Install Task
         uses: go-task/setup-task@01a4adf9db2d14c1de7a560f09170b6e0df736aa # v2.1.0

.github/workflows/push-docker.yml

@@ -78,7 +78,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
 
       - name: Set up Docker Buildx
         id: buildx

.github/workflows/swagger.yml

@@ -48,7 +48,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
 
       - name: Generate Swagger documentation
         run: ./gradlew :stirling-pdf:generateOpenApiDocs

.github/workflows/tauri-build.yml

@@ -122,7 +122,7 @@ jobs:
         uses: Swatinem/rust-cache@c19371144df3bb44fab255c43d04cbc2ab54d1c4 # v2.9.1
         with:
           workspaces: frontend/editor/src-tauri
-          # Stable key shared across workflows so the nightly warmer. 
+          # Stable key shared across workflows so the nightly warmer.
           # rust-cache still appends OS + rustc + Cargo.lock.
           shared-key: tauri-${{ matrix.name }}
           save-if: ${{ github.ref == 'refs/heads/main' }}
@@ -150,7 +150,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
 
       - name: Setup Task
         uses: go-task/setup-task@01a4adf9db2d14c1de7a560f09170b6e0df736aa # v2.1.0

.github/workflows/test-build-docker.yml

@@ -106,7 +106,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
           cache-disabled: true
 
       - name: Install Task

.github/workflows/testdriver.yml

@@ -51,7 +51,7 @@ jobs:
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e # v6.1.0
         with:
-          gradle-version: 9.5.1
+          gradle-version: 9.6.0
 
       - name: Build with Gradle
         run: ./gradlew build